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1. REPORT DATE APR 1974
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4. TITLE AND SUBTITLE Shipbuilding Alignment With Lasers
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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Surface Warfare Center CD Code 2230 - Design Integration ToolsBuilding 192 Room 128-9500 MacArthur Blvd Bethesda, MD 20817-5700
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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18
F O R W A R D
.-. .
This manual is the end product of one of the many research projects being performed underthe National Shipbuilding Research Program. The Prograrn is a cooperative. cost-shared effortbetween the Maritime Administration’s Office of Advanced Ship Development and the shipbuild-
ing industry. The objective. as conceived by the Ship Production Committee of The Society ofNaval Architects and Marine Engineers, emphasizes productivity.
The research effort contained herein is one of the nine outfit Category projects being managedand cost shared by Todd Shipyards Corporation. It was performed in response to the task state-ment titled “Optical Lasers in Shipbuilding”.” The work was assigned by subcontract to the
Boeing Company, after evaluation of several proposals.
Mr. A. K. Creighton of Boeing’s Applied Optics Group. Manufacturing Research and Develop-
ment was the Senior Engineer on the project.
Mr. L. D. Chirillo, Todd Shipyards Corporation, Seattle Division was the Program Manager.
Special acknowledgement is due also to the following for “their constructive criticism of themanual in its draft form: Mr. F. T. ‘Braithwaite, Norfolk Naval Shipyard; Mr. Arthur B. Millay,Sun Shipbuilding and Dry Dock Company; Mr. W. G. Lockett, Mr.Rammell, Newport News Shipbuilding and Dry Dock Company; Mr.A. Williamson,...Mr.” Jack Schaefer, Bethlehem Steel corporation,Shrinivasan;” Seatrain Shipbuilding Corporation.
.
Ed “Basta, Mr. Wayne 0B.Hans Ruehsen, Mr. JohnSparrows Point; Mr. V.
Preceding page blan .
EXECUTIVE SUMMARY
The basic objective of this manual was to present actual experience in applying Iasers forshipbuilding alignment and to identify areas where lasers could be advantageous over othersystems for either alignment or measurement. Inquiries in numerous shipyards disclosed thatthere were a few successful and significant applications, some abortive attempts and virtuaIly nomeaningful cost data related to specific alignment functions.
Those attempts which were not successful are attributed to not having purchased the rightlaser device for the job in hand and to not recognizing that maintaining a power limit; for safety,inhibits use over long ranges in bright daylight.
The initial draft for this manual emphasized detailed alignment procedures. An advisory board,consisting of alignment people from various shipyards, recommended that dependence be placedupon each shipyard’s specific procedures and that the manual serve to facilitate understanding
of the laser devices and accessories so that they could be readily adopted. In place of proceduresthey recommended liberal use of illustrations to suggest applications. This technique was alsobelieved to be better for other reasons.
Lasers are inherently better for alignment measurements that are precise and repeatable overlong distances because they do not depend on human vision to detect and identify the amount ofmisalignment. The visual laser beam minimizes the skill required for establishing planes andangles. But, neither of these characteristics are required in all shipbuilding applications. Lasersare better for virtually all machinery alignment: Yet, converitional optics are sufficiently accurateat short ranges and sometimes prefeired in very bright light. Thus, the general replacement ofexisting optical equipment with lasers is not recommended. Procurement costs are about thesame and many accessories are interchangeable. Therefore, when supplementing existing align-ment equipment it would be prudent to procure lasers in order to allow alignment people toselect and use that which is best for the immediate task in hand.
This manual provides guidance with which to select and specify lasers that serve the suggestedapplications. Moreover, it provides sufficient knowledge for someone already experienced inalignment techniques to adapt lasers to existing procedures and to implement new procedures. Itcan be used to convey and understanding of lasers and their accessories to first-class shipbuilding craftsmen.
P r e c e d i n g p a g e b l a n
One device described herein, the simple laser, is cheap and can be productively applied. Lowpowered lasers are sufficient for most applications and with nominal precautions they do notimpose any hazard. Welding arcs could be more dangerous to the passerby. The U. S. Department of Labor, in putting into effect the Occupation Safety and Health Act (OSHA), has established1 milliwatt per square centimeter as the maximum permissible exposure of continuous laserradiation on the eye. All laser alignment techniques suggested herein necessarily conform to thisstringent limit.
This manual first describes the creation of laser light, the laser beam, typical laser instrumentsused for alignment, and their accessories. At this point, some readers should envision for thems-elves, alignment applications, even new accessories, based on their own experience and needs.Thereafter, use of the laser beam for basic alignment functions are described. The next sectionsdescribe the applications of the foregoing to some typical shipbuilding alignment tasks. Appen-dices are included to provide useful information concerning safety, specifications for buying alaser, etc.
There are alignment techniques other than those suggested herein. Most presented are Repr-esentative of what is now being accomplished by optical means in the shipbuilding industry. It isreiterated that they are intentionally suggestive so that they can be applied in accordance withany detailed alignment procedure preferred by a shipyard.
CONTENTS
1.0 INTRODUCTION . . . . . . . . . . . . . . .
1.1 Laser Light . . . . . . . . . . . . . . .
1.2 Laser Beam Source . . . . . . . . .
1.3 Applying Lasers for Alignment”
Page
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘1
. . . . . . . . . . . . .... . . . . . . . . . . . . . . . . 1
. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.0 ACCESSORIES AND THEIR FUNCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Accessories for Alignment Laser... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Accessories for Transit Laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...30
Accessories for Laser Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Accessories for Laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...35
Establishing Reference Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Establishing Reference Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Establishing Reference Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Measuring Distances From Lines and Planes . . . . . . . . . . . . . . . . . . . . . . . . . 43
Measuring Angles From Reference Lhes and Planes . . . . . . . . . . . . . . . . . . . 45. .Measuring Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..47
3.0 SUGGESTED LASER APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.1 Propulsion Shaft Alignment With Inboard-Accessible Stern Bearing . . . . . . . 503.2 Propulsion Shaft Alignment With Conventional Sterntube . . . . . . . . . . . . . . . 72
3.3 Alignment for Installation of Large Rudders and Rudder Stocks . . . . . . . . . 79
3.4 Hull Structure Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..82
3.5 Ideas for Outfitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
APPENDIX A–Laser Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...94
APPENDIX B–Laser Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...96
APPENDIX C–Visual Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..” . . . . . . . . . . . . . . . ...107
INTRODUCTION
1.1 LASER LIGHT
The name "laser"isformed from the initial letters in the term "light amplificationbystimulated emission of radiation.” It comes. from a proces like that used to generateordinary fluorescent light. A fluorescent lamp features a mercury-vapor-filled glass tube,internally coated with a special powder. An electric. arc within emits invisible ultravioletlight. This light energy is absorbed by the powder which then emits visible light. The lamp“fluoresces, " i.e., its tine particle coating emits radiation in the form of visible light afterbeing stimulated by radiation from another source. .
Physicists explain this phenomenon using the generally known theory that an atom islike a planetary system in which its nucleus replaces the sun and its electrons replace theplanets. They theorize further that, when an atom is stimulated it absorbs energy bywidening its electron orbits. The fl yball weights on a centrifugal governor behave this way.In both cases, when the stimulation is relieved, energy is released until the original energylevels are achieved. For an atom of a particular element, the energy difference is emitted aslight radiation of a definite frequency, i.e., a specific wavelength or color. In a fluorescentlamp, the powder coating is compounded from atoms of different materials. These responddifferently to the stimulation so that the increase and decrease processes take placerandomly. The result of these various wavelengths, emitted without synchronization, issimulated daylight.
The laser uses like atoms having a slight margin of stability at a particular high energylevel and a method of stimulation that can get most atoms “high” simultaneously. One“going off” will trigger all so that they emit synchronizing bursts of light at specificfrequencies. Rapid repetitive bursts produce a steady light source with waves radiated in alldirections. It is coherent, i.e., the waves of one frequency” move through space in “step”with one another. Its energy can be concentrated into a light beam that spreads out littleover a long distance. It is this high intensity. almost parallel, light beam that is ideal foralignment. When created as visible light, it can be detected by placing any material, evenclear glass, in its path. It can also be detected by electronic means.
1.2 LASER BEAM SOURCE
The laser beam source most commonly usedenvelope that contains gaseous elements and aAppendix B.)
Special mirrors are incorporated that are:
for alignment (see Figure 1-1 ) features anmeans of stimulating them. (See also
Designed to reflect selected light of one color
Aligned to reflect only light waves thtit are parallel to the longitudinal axis
Positioned to ensure that the reflected waves are in phase with the oncomingwaves so that they reinforce each other, i.e., me amplified
Silvered to achieve full reflection at one end and partial reflection at the other inorder to permit the steady emergence of sufficiently amplified light waves.2
The laser light source is mounted in a rugged tubular housing, as illustrated in Figure1-2, which:
Provides means for maintaining the careful position and alignment of the mirrors
Incorporates an optical system that further concentrates or “collimates” thediverging rays to form a more parallel light beam.3
Protects the internals and provides a cylinder that, if finished to National AircraftStandards (NAS)4 specifications. would be interchangeable with the accessoriesfor conventional optical telescopes used for alignment.
Often the mixture is of helium and neon. Stimulation cun be started with an electric arc and sustained byapplying radio-frequency voltage. This energizes the hchum utoms that, during collisions, transfer energyto the neon atoms. The latter have the needed “slight margm of stability” necessary for producing laserlight.
2A “pulsed” Imer is designed to prevent the steady emergence of light in order to create a very high energybuildup internally. Special “pulse” techniques release energy that is concentrated enough for burning andwelding applications. It is this type of laser that is extremely hazardous.
Figure I-I: Laser Beam Source
1.3 APPLYING LASERS5 FOR ALIGNMENT
As with all technologies, there is no one tool, no onesatisfy all production requirements for shipbuilding. We
measuring instrument that willneed micrometers for precise
measurement of small items. We need the 6-inch scale for measuring hand-sized parts, andwe need measuring :tapes for measuring large sections. Similarly, one specific laser devicecannot efficiently cover the full spectrum of alignment requirements in shipbuilding.
Terminology for laser beam sources used for alignment varies between users andbetween vendom. To eliminate confusion, the following, purposely concise, definitionsapply throughout this rnanuaI (see also the Glossary):
l The alignment laser is analogous to the alignment telescope, Figure 1-3. Its beam isprecisely centered relative to its NAS finished cylindrical surfaces. The mechanical andoptical axes of the beam’s ori~n coincide.
Alignment Laser Alignment Telescope
($2,000 – $2,500) ($2,200 – $2,700)
(Ako known as.the tooling laseror the precision laser)
Figure I-3: Comparison of Alignment Laser and Alignment Telescope
5"Laser," the acronym for “light amplification by stimulated emission of radiation: which applies to thelightl, is also irr general. use. for designating the device that produces the light.
4
The transit laser is analogous to the transit telescope, Figure 1-4. Its beam is preciselyaligned relative to the viewing axis of the teleicope upon which it is mounted. A modelfitted with transfer optics will project the laser beam coincident With the optical axis, Figure1-5. However, its beam diameter and degree of collinlation for a specific range is dependentupon the telescope’s lens system and focusing capabilities. Its beam is collimated only whenthe telescope is focused at infinity. It can be focused to a very small spot at other ranges.
Figure 1-4: Comparison of Transit Laser and Surveyork Transit Telescope
NCIDENTAXIS
Figure 1-5: Transit Laser With Luser Beam and Telescope Optics Coincident
● The laser Ievel is analogous to the surveyor's level, Figure 1-6. Its beam is preciselyaligned relative to a spirit-level vial.
OPTICAL LINE OF SIGHT J
Laser Level Surveyor’s Level
($1,500 – $2,000) ($1 ,200 – $1 ,400)
Figure I-6: Laser Level Compared With Surveyor's Level
● The laser is analogous to tle .simple telescope. Figure 1-7. Its beam is not aligned to
any reference. The Iuscr housiilg may be rectangular, Figure 1-8.
Laser
($300 – $900)
Telescope
(Known also as the laser headand regular alignment laser)
Figure 1-7: Simpk Laser Compured with Simple Tdescope
Figure I-8: Rectangular Laser Housing
2.0 ACCESSORIES AND THEIR FUNCTIONS
Many accessories that are used for laser devices are the same as those used for optdevices, and they now exist in most shipyards.
2.1 ACCESSORIES FOR ALIGNMENT LASER
2.1.1 SphericaI Adapter
The spherical adapter (Figure 2-1 ) is manufactured to NAS specifications and is used toestablish a spherical reference of known radius around the point where the mechanical andoptical axes of the beam’s origin coincide, Figure 2-2. It is also used to establish the samespherical reference around the center of a visual target or an electronic centering target.Precision measurements can be made from the surface of the spherical adapter.
Spherical adapters with a locking collet can be purchased. The purpose of the lockingcollet is to firmly secure the adapter to the alignment laser.
The spherical adapter may be used with a shipyard-manufacturedmore often it is used in conjunction with the adjustable-cup mount.
jig (Figure 2-3), but
2.1.2 Adjustable-Cup Mount
The adjustable-cup mount (Figure 2-4) facilitates positioning the spherical adapter inany orientation around a permanent reference point. For high accuracy, its base is doweled
in addition to being bolted to the structure upon which it is attached. In other applications,it couId be attached with C-clamps. It is adjustable in one axis over a range of 2-1/2 inches.Men its stem is adjusted and locked, the spherical adapter and other attachments mayberemoved and replaced repetitively without disturbing the reference point. Sights ormeasurements may be made throu~ the hollow adjustable stem.
10
LOCKING SCREW
BASE
Adjustable-Cup Mount
Figure 2-4: Adjustable-Cup Mount and Reference Point Setting Assembly
2.1.3 Holding Clamp
The holding clamp firmly anchors the spherical adapter to the adjustable-cup mount(Figure 24) and is designed to allow maximum access to the sphere’s surface for”measurement purposes.
.
2.1 .4 Reference Po in t Se t t ing Assembly
The reference point setting assembly (Figure 2-4) is used to deliberately fix a referencepoint. Precision measurements can be made by measuring to the surface of the spherical adapter because its center is coincident with the reference point. Once a reference point isset with the assembly, the spherical adapter cin be rotated without disturbing the referencepoint, Figure 2-5.
REFERENCE POINT
2.1.5 Standard Alignment Bracket
The standard alignment bracket is used with a permanently positioned adjustable-cupmount, Figure 2-6. It grasps the alignment laser to prevent axial and rotational movement. Itis provided with precision adjusting screws for rotational adjustment about the referencepoint within the spherical adapter.
ADJUSTING SCREWS
f
Figure 2-6: Holding Bracket for Alignment Laser
12
Variations of the standard alignment brwket can be easily manufactured in theshipyard, Figure 2-7. Selection of a specific bracket is dependent upon a particularalignment application.
Vee Blocks
Universal Bracket Modified StandardBracket
Figure 2-7:
2.1.6 Adjustable Target Holder [Spider]
The adjustable target is a type of bracket (Figure 2-8) designed to support andfacilitate adjustment of a target within the center of a cylinder. Some are fitted withattached inside micrometers or dial indicators that facilitate centering. Normally. they areavailable as a single kit useful for 16- to 68-inch diameters.
14
Figure 2-8: Adjustable Target Holder
2.1.7 Vertical Holding Bracket
The vertical holding bracket is equipped with spirit levels and adjusting screws thatfacilitate projecting the laser beam vertically, Figure 2-9.
SPIRIT LEVEL
Figure 2-9: Vertical Holding Bracket for Alignment Laser
2.1.8 Electronic Centering Detector (Electronic Target )
This detector consists of a disc-shaped light-sensitive photo cell that is divided into fourequal parts. The voltages generated by the quadrant cells when struck-by laser light arecompared in a redout box equipped with meters. indicating horizontal and verticaldisplacement, Figure 2-10. The enclosed circuitry operates on the null principle, i.e., whenthe laser beam falls equally on each quadrant cell of diagonally opposite pairs, equal andopposing volttges arc generatcd. There is no subsequent current flow: the appropriate meterwill remain at zero indicating true center. When the laser beam is off center. the opposingvoltages will be unequal causing a current flow that can be read on a calibrated meter in anyconvenient increment of linew measure, Figure 2-11.
Normally. electronic centering detector systems are provided as part of a precisionalignment kit that includes an alignment laser and at least two matched electronic targetsand a readout box. Generally. all components should be purchased from the samemanufacturer. Accuracies as fine as 0.0001 inch are possible. Even with the greatertolerances allowed in shipbuilding. there should be assurance that the electronic targets arematched with a specific alignment loser.
The housing of the electronic centering detector is dimensioned in accordance withNAS specifications. [t is provided with a flange that ensures precise location of thelight-sensitive surface at the center of a spherical adapter, Figure 2-12.
18
2.1.9 See-Through Detector
The see-through detector (Figure 2-1 3) is an electronic target that uses a beam splitter
to divert some light energy for sensing while permitting the remainder to continue, Thereshould be assurance that they are mtitched with a specific alignment laser.
Figure 2-13: See -Througll Electronic Detector
2.1.10 Single-Axis Electronic Detector (Wand)
The single-axis electronic detector (Figure” 2-1 4) employs a split photo cell, amicroammeter, and a null circuit. When the microammeter reads zero, i.e.. at null, the laserbeam is evenly divided on each half of the photo cell. When in this condition. themeasurement is read directly off the attached measuring device.
2.1.11 Visual Targets
Visual targets (Figure 2-1 5) are cheap to make and can be easily manufactured in ashipyard. Accuracies better than 1/32 inch ‘or 1 millimeter can readily be achieved if thetargets are shielded from bright light and if each target hole diameter is matched to thebeam diameter at a specific location.
Transparent and translucent materials are best becimse. when properly shaped, theyscatter or diffuse intercepted laser light. (See Appendix C for manufacturing details. )
TRANSPARENT
r
ACRYLIC TARGET(Sliced view shown for clarity)
Figure 2-15: Visual Targets
20
2.1.12 Autoreflecting Head
The autoreflecting head (Figure 2-16) attaches to the alignment laser used as the beamsource. It is primarily for detecting the center Of the same beam when it is reflected backfrom a mirror. Centering with the autorefkting’ head ensures that the returning beam iscoincident with the exiting beam and that both are perpendicular to the mirror’s surface.
COLLIMATINGRETURNING BEAMCOINCIDENT WITHPROJECTED BEAM
9
RETURNING BEAM
d
MIRRORELECTRONICDETECTOR
2.1.13 Autocollimating Head
The autocollimating head (Figure 2-17) is a built-in feature that serves the samepurposes as the autoreflecting head except that it is more accurate when the beam sourceand mirror are less than 10 feet or 3 meters apart. It has an additional capability formeasuring small angles.
ALIGNMENT LASER OBJECTIVE LENS OF AUTOCOLLIMATINGHOUSING LENS SYSTEM
R E T U RN I N G B E A M
at a distance equivalent to the focal length of the objective lens.
Figure 2- I 7: Alignment Laser Auto colIimating Head
22
2.1.14 Vertical-Hanging Leveling Mirror
This mirror is a precision mirror delicately balanced and suspended so that it is in atrue vertical plane. A beam made perpendicular to it, as by autoreflection or autocollima-tion, will be level, Figure 2-18.
The vertical-hanging leveling mirror may also be used to redirect a laser beam in any
direction about a level reference, Figure 2-19.
2.1.15 First-Surface Precision Mirror
The first-surface precision mirror (Figure 2-20) is fitted with a magnetic, spindle, or
other types of mounting adapters that establish it as parallel to a reference plane orperpendicular to a reference axis. Some are fitted with adjusting screws so that they maybe
skewed..
A beam can be made perpendicular to a mirror surface by autoreflection or
autocollirnation. A mirrorits surface.
Magnetic Mounted
can be used to redirect a laser beam
Spindle Mounted
about
SCREWS. 120° APART
MIRROR
Figure 2-20: First-Surface Precision Mirror
24
a line perpendicular to
Plate Mountad
2.1.116 Optical Square
The optical square (Figure 2-21 ) is attached to the aiignment laser and is used toestabiish a beam perpendicular to a reference beam. The opticiii square is avaiiable in variedconfigurations. However, they are all equipped with a sphere that is ground to NASspecifications. The sphere can be mounted on the adjustable-cup mount.
2.1.17 Planing Prism
The planing prism is a very precise device. It generates planes by rotation of a prism,Figure 2-22. The axis about which the prism rotates must be precisely adjustedperpendicular to the Iaser beam before use. This limits its application to beam sources thathave an autoreflecting or autocollimating capability.
PLANING PRlSMLASER
I
9 —
I
The planing prism is equipped with an end mirror necessary for orienting the plane tobe generated perpendicular to a reference beam, Figure 2-23. Necessarily, the referencebeam source must also have an autoreflecting or autocollirnating capability.
2.1.18 Planing Penta Prism
The planing penta prism is used to generate planes perpendicular to a remotely locatedlaser beam source. It is a precisely manufactured device that functions by rotation of aprism in precision bearings, Figure 2-24. The axis about which the prism rotates must havethe beam aligned to the center of the entrance and exit orifices to ensure perpendicularity.For the greatest accuracy, it should be aligned with an autocollimating laser source.
Figure 2-24: Planing Penta Prism
2.1.19 Mounting Bases
Portable Standfor Flat Floor
Portable-Standfor Rough Floor (Welded in Place)
Permanent Standfor Wet Areas
(Cement)
Figure 2-25: Mounting Bases
2..2 ACCESSORIES FOR TRANSIT LASER
2.2.1 Calibration Target
The calibration target (Figure 2-26) is peculiar to that transit laser designed to have itslaser beam parallel to itsensure that the laser beam
2.2.2 Fan-Beam Lens
optical line of sight. The calibrationand optical line of sight are parallel.
target is the device used to
The fan-beam lens (Figure 2-27) focuses the single-line beam into a thin fan-shapedbeam. Because its energy is dispersed throughout the fan, it must be used in subdued lightand at relativel y short ranges.
2.2.3 Applying Alignment Laser Accessories
Alignment laser accessories that can be used with the transit laser are:
●
●
●
●
●
●
●
●
●
•
Reference point setting assembly (Figure 24), for holding a target only .
Adjustable target holder (Figure 2-8)
Electronic centering detector–electronic target (Figure 2-1 O)–provided there isassurance that the electronic targets are matched with the laser
See-through detector (Figure 2-1 3);povided that they are matched with the laser
Single-axis electronic detector–wand (Figure 2-1 4)
Visual targets (Figure 2-15), supplemented by those illustrated in Figure 2-28
Vertical-hanging leveling mirror (Figures 2-17 and 2-19)
First-surface precision mirror (Figure 2-20)
Planing penta prism (Figure 2-24)
Mounting bases (Figure 2-25), provided adapters are employed, Figure 2-29.
30
2.3 ACCESSORIES FOR LASER LEVEL
Accessories for the laser level are identical to those specified for the laser transit exceptfor the calibration target. .
34
2.4 ACCESSORIES FOR LASER
Alignment laser accessories that can be used with the laser are:
Reference point setting assembly (Figure 24) for holding visual targets only
Adjustable target holder (Figure 2-8) for holding visual targets only
Single-axis electronic detector–wand (Figure 2-1 4)-for use over a limited rangewhere the beam diameter is commensurate with the photo cell aperture
Visual targets illustrated in both Figures 2-15 and 2-28
Vertical-hanging mirror (Figures 2-18 and 2-19)
First-surface precision mirror (Figure 2-20)
Planing penta prism (Figure 2-24) for use over a limited range where beamdiameter is commensurate with prism aperture
Mounting bases (Figure 2-25) for use in conjunction with vee blocks or universalbrackets (Figure 2-7)
2.5 ESTABLISHING REFERENCE POINTS
A reference point is defined by the interception of a line and a plane. The alignment
laser, transit laser, level, and simple laser are all useful for this application.
I\ “
+
LASERSPHERICAL BEAMA D A P T E R ~ i ’
%
ABLE-CUP
Figure 2-30: Establishing a Reference Point With the Alignment Laser
2.6.3 With the Laser Level
Only level reference lines may be established with the laser leveI. Its application isidentical to that for the transit laser except that it is limited to use with monuments existingin a bulkhead only, for example, the walls of a graving dock.
2.6.4 With the Laser
STICK-ON VISUAL TARGET
POINT A
VISUAL TARGET
LASER
REFERENCE POINT SETTINGASSEMBLY OR OTHER TARGETHOLDER
UNIVERSAL OR OTHER BRACKET
Figure 2-33: Establishing Reference Lines With the Simple Laser
2.7.2 With the Laser Transit
LBASIC uREFERENCE LINE
. .
HORIZONTALPLANE
RANSITASER
REFERENCE LINE
u
~FAN BEAM LENS
~ BASICREFERENCE LINE
I
● The plane may be skewedto any orientation.
TRANSI T. LASER
Figure2-35: Establishing Reference Planes With the Transit Laser
2.7.3 With the Laser Level
A plane may be generated precisely with the laser level in its horizontal orientationonly. The fan-beam lens can also be adapted to generate skewed planes around horizontallines only.
2.7.4 With the Laser
R E F E R E N C E LINE
GENERATED 1
Figure 2-36: Establishing Reference Planes With the Simple Laser
42
- R E F E R E C E B E A M
l The electronic centering detector (electronic target) measures displacementof the beam from two axes. It measures in fine increments and in some systemsthrough a range up to 1/2 inch.
DISPLACEMENT FROMHORIZONTAL AXIS ASREAD FROM METER
.DISPLACEMENT FROMVERTICAL AXIS ASREAD FROM METER
Figure 2-38: Measuring Distances from Reference Lines and Planes
. . , .
.
The laser interferometer (Fi@emeasuring device. It is calibrated for
2-42) is a highly precise, relatively expensive, linearuse with a special reflecting target and is limited to
measuring distances traversed by the target over a very precise straight-line path. They canachieve better than *0.000 1-inch accuracy. Application is suggested for:
Linear measurement on machine tools having precisely finished rails or ways
Verification of linear control devices. such as in numerical. control burningmachines
Use as a linear measurement standard by quality-control people
Eventually, use as a follow-up device to override the stepping-motor system in
numerical control machines.
Figure 2-42: Laser Interferometer Precise Distance Measuring Equipment
48
It appears that,as of mid-1973. at least for the near future. nonlaser devices such as theelectromechanical measuring tape (Figure 2-43) are far more practical for shipbuildingapplications. These are accurate to # 0.00 1‘inch over a range from O to 20 feet. They can beobtained for greater ranges. Application is suggested for situations where the digital readoutcapability is advantageous.
Figure 2-43: Electromechanical Distance Measuring Device
3.1
3.0 SUGGESTED LASER APPLICATIONS
PROPULSION SHAFT ALIGNMENT WITH INBOARD-ACCESSIBLESTERN BEARING
3.1.1 Establishing a Reference Line Using Fixed Shipboard and/or Dock References
See Figure 3-1.
3.1.2 Joining the Stern Bearing Tunnel Section Erection Unit
See Figure 3-1.
The visual targets C and D are instilled in the shop:
On tiie axis of the tunnel if it is to be installed concentric with reference line AB
Offset from the axis of the tunnel if the tunnel is to be installed other thanconcentric to reference line AB.
Visual targets properly designed for the distances they are used from the beam sourcewill readily detect deviations of # 1 millimeter (see Appendix C). Normally, both targets canhave the same diameter holes if they are within 50 feet of each other. Visual targets shouldbe observed continually to monitor any movement of tunnel alignment during welding ofthe erection unit and until completion of all other welding in the vicinity.
50
3.1.3 Re-establishing the Repulsion-Shaft Reference Lineto the Joined Stern Bearing Tunnel Erection Unit
The reference line has to be re-established based on the actual position of the stembearing tunnel achieved. Depending on a particular shipyard’s procedure, the reestablishedline will be used either for first positioning the after-frame ring or for first positioning thereduction gear. In both cases, since machinery tolerances are generally *0.005 inch, analignment laser and electronic targets should be used to establish:
1 Reference line for first positioning the after stem ring, see Figure 3-2
l Reference line for first positioning the reduction gear (solid shaft), see Figure 3-3
l Reference line for first positioning the reduction gear (hollow shaft), see oFigure 3-4
l Reference line if the reduction gear foundation is to be finished neat, seeFigure 3-5
52
Figure 3-5: Establishing a Reference Line if Reduction Gear Foundation Is To BeFinished Neat
56
3.1.4 Attaching the After-Frame Ring
Positioning and maintaining alignment during welding of the machine-finishedafter-frame ring requires precision techniques. Because the after-frame ring is relativelyshort, the two points required to control its alignment are relatively close to each other.Consideration must be given to avoid parallactic error, Figure 3-6.
Two methods are possible. The preferred method (Figure 3-7) employs “a mirrormounted in a precision jig, a” see-through electronic target, and either an autocollimating orautoreflecting alignment laser. An inherent advantage with the mirror is that the angledetected is easier to read because it is always twice-the angle being measured, Figure 3-8.The second method (Figure 3-9) can be accomplished with an ordinary electronic target, asee-through electronic target, and without either autocollimating or autoreflecting capa-bility, provided the alignment laser is relocated’ as close as practicable to the after-framering. Sometimes this is not desirable because of access required and adverse effects ofwelding in the vicinity.
3.1.5 Aligning the Reduction Gear (Solid Shaft )
Either of two shipyard-manufactured jigs could be used, i.e., an electronic target andmirror holding jig (Figure 3-10) or an alignment-laser holding jig (Figure 3-1 1). The formeris used when the reference beam is directed toward the reduction gear; the latter is usedwhen it is desired to mount the laser source on the reduction gear and direct it aft.
Alternate use of the electronic target and mirror for centering and orienting thereduction-gear flange perpendicular to a reference beam is illustrated in Figure 3-12.Further, this figure illustrates how the reduction gear may be displaced from or set at anangle to a reference beam. Note. as illustrated in Figure 2-12, the electronic target hasvertical and horizontal axes. The two readout meters correspond to these axes. If, for anyreason, the reduction gear was rotated, care must be taken to interpret the meters as repre-senting axes that have also been rotated.
Use of an alignment-laser holding jig is shown in Figure 3-13. Figure 3-14 illustrateshow the reduction gear may be displaced from or set at an angle to a reference beam.
Adjust laser bracket to roughly align beam con-centric with shaft axis.Rotate shaft and adjust the laser bracket until the“spot” remains stationary on white card: thisassures that beam is concentric with shaft axis.
Figure 3-13: Bull Gear Rotated to Align Laser to Shaft Axis
Figure 3-14: Measuring Displacement and Angular Relationships With SolidPropulsion Shaft
3.1.6 Aligning the Reduction Gear (Hollow Shaft ) .
This method is illustrated in Figures 3-15 and 3-16. Uniquely, the laser beam is fixed
relative to the reduction gem. Figure 3-15 illustrates how to compensate for deflection of the
shaft due to the bull gear mass. This is achieved by establishing the reference beam with
respect to the shaft centerline only at the center of bull bearing reactions. The entire gear is
manipulated until the beam is oriented as required with respect to the two known reference
points, A and B, see Figure 3-16.
REFERENCE AXIS
IELECTRONICSEE-THROUGHTARGET LOCATEDAT CENTER OFBEARING REACTION C
Figure 3-15: Establishing Bull Gear Shaft Axis
66
Figure 3-16: Positioning Reduction Gear (Ho1[ow Shaft)
3.1.7 Positioning of Line Shaft Bearings or Temporary Shaft Supports
Depending upon the alignment procedures prescribed in a shipyard, the techniquesillustrated in Figure 3-17 can be used to achieve initial or final positioning of the line-shaftbearings. Where dependence is placed on find positioning by measuring “sags and gapS” (or“drops and openings”) and/or by actually weighing for determining bearing reactions, thevisual targets (Figure 2-1 5) could be used for initial alignment within *0.020 inch. With areasonable degree of skill, they could achieve accuracies of *0.005 inch in this application.Use of electronic targets (Figures 2-11.2-12. and 2-13) eliminates all human judgments, andabsolute accuracies of *0.001 inch are possible.
68
3.1.8 Checking Alignment of Installed Shaft
Checking A lignment Qf- Installed Shaft
70
R E A D O
Figure 3-19: Permanent References for Re-establishing Alignment
3.2 PROPULSION SHAFT ALIGNMENT WITH CONVENTIONAL STERNTUBE
3.2.1 Establishing a Reference Line
See Figure 3-20.
3.2.2 Joining Sterntube Erection Unit ( or Sterntube if Installed Separately)
See Figure 3-20.
Visual targets C and D can be installed in the shop:
● On the axis of the sterntube if it is to be installed concentric with referenceline AB
● Offset from the axis of the sterntube if the sterntube is to be installed other thanconcentric to reference line AB.
Visual targets properly designed for the distances they are located from the beamsource will readily detect deviations of *1 millimeter (see Appendix C). Normally, bothtargets can have the same diameter holes if they are within 50 feet of each other.
Visual targets should be observed continually to monitor any movement of sterntubealignment during welding of the erection unit and until completion of all other welding inthe vicinity.
3.2.3 Re-establishing Propulsion-Shaft Reference Line to Joined Sterntube
The reference line has to be re-established based on the actual position of the sterntubeachieved. Depending upon a particular shipyard’s procedure, the re-established line will beused either for first boring the sterntube or for first positioning the reduction gear. In bothcases, since machinery tolerances are generally 0.005 inch, an alignment laser andelectronic targets should be used to establish:
● Reference line for first boring the sterntube. see Figure 3-21.
● Reference line for first positioning the reduction gear (solid shaft), seeFigure 3-22.
● Reference line for first positioning the reduction gear (hoIlow shaft), see Figures3-23 and 3-24.
3.2.4 Aligning Reduction Gear, Positioning Line Shaft Bearings. and Checking Alignmentof Installed Shaft and Permanent References for Re-establishing Shaft Alignment
See Sections 3.1.5 through 3.1.9 and Figures 3-3 through 3-19, respectively.
. . - .:.
74
welding in the vicinity, a newreference line, A 1 B is establishedusing the sterntube boring jig anda shipyard-manufactured adapterto support an autocollimating orautoreflecting alignment laser”
A l
l If necessary, usinga see-through electronictarget, locate anotherpoint B1 somewhere aftof the reduction gear.
PYARD-MANUFACTURED JIGHOLD ELECTRONIC TARGETMIRROR (SEE FIGURE 3-10)
REFLECTED
Figure 3-22: Establishing a Reference Line First Positioning ReductionGear (Solid Shaft)
76
l
Following completion of weldingin the vicinity, a new referenceline Al B is established using thesterntube boring jig and a shipyard-manufactured adapter to supportan electronic target.
A l
The single-axis electronicdetector (wand) is used to verify
throughout the sterntube. (Alternately, a spider could beused to support a target at theforward end of the sterntube.)
ALIGNMENTLASER
If the adjustable-cupmount is not removed,point A could be easilyre-established if required,
If point B is aft and clear of the reduction-gear site, simply substitute a see-throughtarget for the alignment laser. If not, using asee through target, establish B 1 beforeremoving the alignment laser from point B.
Figure 3-23: Establisihing a Reference Line for First Positioning ReductionGear {Hollow Shaft)
Figure 3-24: Establishing a Reference Line First Positioning ReductionGear (HO11O Shaft)
78
●
3.3 ALIGNMENT FOR INSTALLATION OF LARGE RUDDERS AND RUDDER STOCKS
4
/
r
Figure 3-26: Aligning Rudder Stock Keys to Keyways in Rudder Casting
(based upon an actual application).
3.4 HULL STRUCTURE ALIGNMENT
3.4.1 General
For hull structure. lasers would only be more productive than conventional optics when:
●
●
●
●
●
●
●
Two or more people need access to the reference beam at the same time.
An object has to be positioned with respect to a fixed reference line.
Establishing a plane or measuring deviations from a reference planeline.
The reference line must pass through small openings.
There are poor ambient lighting conditions.
The reference line has to be redirected as with a prism orprism is remote from the instrument.
Using the beam as a pointer to position “punch” marks.
3.4.2 Practical Ranges
Since much of the hull structure alignment would take placeclearly understood that:
or reference
mirror and the mirror or
in daylight, it should be
● With a decrease in lighting due to shadows or on-coming darkness, it becomesmore difficult to sight optically. whereas sighting with a laser becomes lessdifficult.
● With increasing ambient brightness, the optical sighting will improve and thefollowing range limits will be imposed on practical use of existing lasers due to theimposed l-milliwatt limitation by OSHA as of 1973.
● 100 feet with the observer located at laser source
● 600 feet with the observer located at the target site.
3.4.3 Typical Hull Structure Alignment Tasks
3.4.3.1 Establishing Base Plane and Keel Reference Line
See Figures 3-27,3-28. and 3-29.
Figure 3-27:
PLANE
Establishing Keel Reference Plane andLine
3.4.3.2 Controlling Dimensions in Subassembly Fabrication: See Figures 3-30 and 3-31
l A tooling dock usedfacilitates the assemblyfor alignment purposes.
Necessarily, the dock
for aircraft manufactur and alreadyof hull modules. The clock provides
applied to shipbuilding in Japan,access to locations that are best
structure must be stiffened commensurate with the accuracy required.It may be rather elaborate as illustrated in Figure 3-30 or it could simply consist of 4-poles. Theinterior structure of a building could serve provided it does not deflect during crane movements.
The dock structure could also serve to contain ladders and staginga folding or sliding roof, power units for welding, lighting. etc.
for access to the module,
Figure 3-30: Applying a Tooling Dock
Simple laser establishes reference line through visual targets at A & B.
Erection unit is aligned to reference line using visual targets at C & D, the process isrepeated elsewhere as required.
.
Figurc 3-31: Portable Tooling Dock precise Subassembly Fabrication
86
3.4.3.3 Providing Reference Lines and Planes Before Modules Are RemovedFrom Erection Sites
See Figures 3-32.3-33, and 3-34.
End view E n d v i e w
● Three reference points are required; See Figure 3-33.
Figure .3-32: Providing Reference Lines to Monitor Racking and Twisting
‘.
WAND OR VISUAL TARGET
●
●
For nonlevel ships, reference points must be established from the surrounding structure.The planing prism and the alignment laser are used to establish the reference lines andplanes from these points. The same setups as shown in Figures 3-35, and 3-36 canbe used.
A shipyard-manufactured device, such as shown in Figure 2-40, could be used in thisapplication also.
Figure 3-37: Establishing Plumb Reference Line for Positioning Container Guides
3.4.3.5 Aligning ‘Relatively Long Horizontal Rails
E l e c t r o n i c O RV I S U A L T A R G E T
● Asimple Iaser can be substitutedfor the alignment laser and visualtargets for the electronic targetsin cases where # /1 6-inch accuracyover 200 feet is adequate. Withthe alignment laser, accuracy of
2 0 0 f e e t .
3.5 IDEAS FOR OUTFITTING APPLICATIONS
1)
2)
3 )
4 )
5)
6)
Reference lines are more easily transferred throughout the interior structure asthe ship is erected because the laser beam:
● Is visible in most interior lighting conditions
● Is readily bent with prisms
● Establishes a visible reference point when intercepted by a bulkhead or deck.
The transit laser would be used in place of a transit telescope.
Striking waterlines on concave surfaces, such as a flared bow, is facilitated. Thisrequires establishing a laser level at a specified elevation at. an approximate radiusthat is representative of the concave surface.
Reference lines can be readily placed in the precise location of a piping run or ofsome other distributive system. Should it become necessary to locate penetrationsin beams offset from this reference line, a single-axis detector (wand) orshipyard-manufactured visual wand or gage could be used to establish a parallelreference line.. In this application, the intercept of the beam by bulkheads anddecks establishes the locations for this penetration. The simple laser, mounted inany method described in this manual, could be used.
False decks, false ceilings. and grounds for bulkhead sheathing can be done in amanner similar to that described for finishing a reduction gear foundation neat(Figure 3-5) or for establishing the bottom plane for a container ship guideinstallation, Figures 3-36 and 3-37. A simple laser could be adapted to this use byadding a shipyard-manufactured jig similar to the one in Figure 2-36, provided itis equipped with a spirit level. The transit laser is, of course, ideal to use in theseapplications. The laser level would be limited to horizontal planes such as for falsedecks and ceilings.
The simple laser equipped with a fan beam lens (Figure 2-27) can be used toestablish a reference plane that would facilitate detecting warpage in structureprior to installation of relatively large doors. windows, and hatches.
The simple laser can readily substitute for a “piano” wire when establishingreference lines for layout of food service equipment, windows, ports,furniture, etc.
APPENDIX A
LASER SAFETY
As of mid-l 973, a proposed safety standard for laser use is being considered by theDepartment of Health, Education. and Welfare Industry Advisory Committee. The proposedstandard lists four classes of lasers as follows:
● Class II:
Cass I:
● Classes IIIand IV:
Lasers with a power output of less than abe exempt from the standard.
Lasers in this class could emit no more
microwatt would
than 1 milliwattpower output. This class would not be considered dangerousbut would have to carry a label cautioning the users not tostare at the laser beam.
These two classes would include all lasers in excess of 1milliwatt of power. Class III would be considered potentiallyhazardous to the eye, and Class IV would be consideredhazardous to the skin. Class III and IV devices would have tobe shielded from the human eye. They also could not be usedfor such purposes as demonstrations, surveying, leveling, oralignment.
Lasers to be used for alignment purposes are assigned to Class II. Thus, they cannotemit power exceeding 1 milliwatt.
Since OSHA has established 1 milliwatt per square centimeter as the maximumpermissible exposure of continuous laser radiation on the eye. the minimum allowed laserbeam diameter is related to the power emitted. For a maximum l-milliwatt power laser, thebeam diameter cannot be less than 1 1.25 millimeters, which corresponds to an area of 1square centimeter. Laser devices built to this maximum power density cannot legally becollimated to a smaller diameter.
94
Precautions that should be observed when using a Class II for for alignment purposes
Post areas with adequate caution signs.
Ensure that the laser power supply and laser housing are electrically groundedbefore electrical power is applied.
Avoid pointing the laser in any direction where a person could stare into thebeam.
Align the beam at a height below or above the normal eye level.
Never leave an operating laser unattended.
Never reflect a laser beam off a mirror or any other polished reflective surfaceindiscriminately.
APPENDIX BLASER SPECIFICATIONS
The following specifications for lasers are furnished as a guide only and not as anendorsement of any make of laser. It is the responsibility of of concerned individuals to testand evaluate the lasers to determine
SUGGESTED ALIGNMENT LASER
which are best suited for their individual applications.
SPECIFICATIONS
Figures B-1 and B-2 show what is commonly called the alignment laser. This group oflasers conforms to National Aircraft Standards (NAS). They have a cylindrical housing thatis either a ground and hardened surface throughout or they have hardened steel mountingrings that are ground. The diameter of the barrel or of the mounting rings is held to atolerance of 2.2498 to 2.2493 inches. This is the same diameter as the housing of thealignment telescope. Therefore, the tooling laser will fit any of the optical tooling alignmentaccessories that were designed around the NAS standards for the alignment telescope. Inmost cases, the alignment lasers will replace the alignment telescope without any additionalcosts in support accessories. The aiignmen laser is well suited for the precision alignmentrequired for machinery and shaft installation.
Some alignment lasers have modulated laser beams. The modulation frequency is 10kHz and its purpose is to eliminate ambient light interference with the electronic targets.Also. some lasers use autoreflection and others use atutocollimation. Autocollimation ismore accurate at closer ranges. is sensitive to angular measurement. and is not responsive todisplacement.
Suggested specifications are:
Output: 1 milliwatt6
Outside
6The output of most lasers can be adjusted. Also. a neutral density filter can be used to reduce poweroutput.
7This specification applies to the whole barrel or to mounting rings. These surfaces must be hardened forwear resistance.
96
Thermostable
S e a l e d a g a i n s t e n v i r o n m e n t
Ruggedly constructed to prevent mirror shift during normal shipyard use
Power cord to laser shielded against accidental cutting and mounted integrally tothe laser
Long-life laser tube with at least a 1-year warranty.
The power pack of the laser should be small, rugged, adequately fused, and haveindicator lights. The indicator lights provide a safety factor since they indicate when thepower pack is energized and when the laser is energized. Power packs available can be usedwith a 117-volt ac source; others can be operated with 12-volt batteries.
New models of the electronic detectors and their readout boxes make precision
alignment easier and more accurate than was previously experienced. Based on this. newadvance of laser detector design, suggested specifications are:
Easily readable meters (Figures B-1 and B-2) indicating horizontal and verticald i s p l a c e m e n t .
A range selection switch to read in 0.001- to 0.005-inch increments.
A light that indicates when the laser beam is striking the detector. This is usuallycalled an acquisition light. The light is necessary for longdistance work when theoperator cannot see his detector very well because of the distance. If both themeters read zero and the laser beam was not striking the detector, he mayerroneously assume the laser beam is centered on the detector. The acquisitionlight eliminates this problem.
Automatic gain control This feature prevents change in laser output power fromaffecting the readout on the meter. Thus, the unit would not require calibrationeach time it was used or when the beam was passed through a prism or other glass.
Two readout modes (fast and slow) are useful features.
An integrating or time-delay readout system. This feature “smooths” out thejumping of the laser beam due to vibrations and changes in air density across thepath of the beam.
● The readout box should be equipped with jack plugs so the readings can berecorded on a strip chart or other recording devices. This is a valuable feature forrecording shaft alignment for customer information, etc.; for measuring thewarping of a ship section over a period of time; or for recording changes in shipstructure after launching.
● The readout box should be equipped to operate from 12-volt battery or 117-voltac power sources.
SUGGESTED SPECIFICATIONS FOR SIMPLE LASER
General specifications for the simple laser (Figure B-3) are:
Barrel should be cylindrical in shape.
The power output should be 1 milliwatt.
The laser must be of rugged construction and be able to withstand the abuse ofthe shipbuilding environment.
The electrical cable from the power pack to the laser must be shielded to preventaccidental cutting. The cable must be made an integral part of the laser housing.
The laser must be sealed against the out-ofdoors environment.
The laser tube should have at least a l-year warranty.
The laser beam diameter for the lower cost lasers are small, being about 1 or 2millimeters (1/16 inch) in diameter. The beam spreads to 1 inch at 100 feet. Somemanufacturers make a collimating lens system that attaches to the laser housing.This collimating unit expands the beam about 10 times and collimates it.
Laser beam divergence is usually listed in milliradians, and most low-cost lasershave divergence of about 0.6 to 0.9 milliradians. The smaller this value, the better.For instance. a 0.85 -milliradian beam divergence would produce about a3-inchdiameter beam spot at 300 feet, whereas a collimated beam of 10millimeters would be about 13 millimeters (1/2 inch) at 300 feet. At 50 feet, the0.85-millirudian divergence beam would be 1 /2 inch in diameter; thus, it dependson application of the laser.
The laser must be operable in any position.
The following list is only a sampling of laser manufacturers. Consult the Laser SuppliesDirectory, which is available in most libraries. for a complete listing of laser manufacturers.The Thomas Registry is another source for this information.
Keuffel & Esser Company20 Whippany RoadMorristown, New Jersey 07960
Laser Alignment & Control Inc.P.O. Box 1093Palo Alto, California 94302
Petrologic Instruments143 Harding Ave.Bellmawr, New Jersey 08030
RCANew Holland Ave.Lancaster, Pennsylvania 17604
Spectra-Physics Company1250 W. MiddlefieldMt. View, California 94040
Coherent Radiation Company3210 Porter DrivePalo Alto, California 94304
Constructors Supply Company15629 CIanton CircleSanta Fe Springs, California 90670
C. W. Radiation111 Ortega Ave.Mt. View, California 94040
Electro Optics Associates901 California Ave.Palo Alto, California 94303
W.& L. E. Gurley CompanyTroy, New York 12181
Hughes Aircraft Co.Electron Dynamics Div.Torrance, California 90509
These laser manufacturers provided the photographs used in this document.
APPENDIX CVISUAL TARGETS
The visual target and the stick-on targets are shipyard-manufactured items. The size of
the targets is dependent upon the distance of the target from the observer and the size ofthe laser beam at the target site. Tables C-1 tind C-11 provide the necessary data for
Fabrication of the targets. An attempt has been made to limit the number of sizes required
for the various distances. Thus, as seen in Tables C-1 and C-II. three target sizes will span thetotal distance of 400 feet. Figures C-1, C-2, and C-3 provide the fabrication instructions forthe targets.
102
1
G L O S S A R Y
ALIGNMENTmounted
LASER: A specially manufactured laser where a helium-neon laser tube isin a cylindrical housing that is machined to NAS specifications. The NAS
specifications are specific dimensions called our for fabrication of the outer diameterof the laser housing. The laser beam is centered on the mechanical axis of the housingto within 0.001 inch. The laser beam diameter remains fairly constant over thedesigned working distance of the laser. It is used for precision alignment.
ALIGNMENT TELESCOPE: A precision refracting telescope containing cross hairs wherethe optical and mechanical axes are made coincident. The optics are mounted in a steelcylindrical housing machined to NAS specifications. It. usually has two opticalmicrometers. It is used in precision alignment work.
AUTOCOLLIMATION: A technique used in alignment whereby a light is reflected back onitself from a mirrored surface to obtain perpendicularity to that surface. The term is
used with alignment telescopes and alignment lasers that are equipped withautocollimating attachments. Thus, an autocollimating laser can detect the laser lightreflected back into it from a mirror surface, If the mirror is tilted, the returning beamwill be offcenter on the photo cell in the laser. thus indicating an angular error.
AUTOREFLECTION: Autoreflection is similar to autocollimation as far as laser applica-tion is concerned: i.e., laser light is reflected back from a mirror and is detected insidethe laser housing. However, the autoreflecting laser does not use lenses in theautoreflecting head, as does the autocollimating laser; thus, it is not a true angularmeasuring device as is the autocolIimating laser.
BEAM BENDING: The term “beam bending” is applied when the direction of the laserbeam is changed. A mirror or prism, etc.. when placed in the path of a laser beam, willbend the laser beam in any desired direction.
BEAM DIVERGENCE: Beam divergence pertains to the spreading of the laser beam as itleaves the laser. Precision lasers employ additional optics to control the spread of thebeam.
107
BEAM, LASER: The laser beam is made up of concentrated rays of light emitted from thelaser source.
BEAM SPLITTER: The beam splitter is an optical device that splits the beam of light intotwo or more beams. The beam splitter can be designed so that the beam can be splitinto two equally intense beams or into unequally intense beams.
COHERENT RADIATION: The term “coherent radiation,” as applied to laser light, refersto the individual light rays that make up the laser beam. All the rays are in phase witheach other. This as compdred with regular red light as it is emitted from a source wherethe individual rays of light are out of phase with each other.
COLLIMATED LIGHT: Collimation pertains to parallelism, thus, a collimated light wouldhave all of the individual rays parallel with each other. Light reaching the earth from adistant star is said to be collimated since only the parallel light rays would reach therelatively small surface of the earth.
ELECTROMAGNETIC RADIATION: Electromtignetic radiation pertains to all forms ofradiant energy from the extremely short wavelength cosmic rays to the extremely longwave radio broadcasting signals. The visual spectrum occupies a very small portion ofthis vast spectrum. Helium-neon laser light is included in the visual spectrum at thelower end (longer wavelength) of the visual spectrum.
FIRST-SURFACE MIRROR: A mirror that has the outside surface of the glass aluminizedto retlect light rather than the back side of the glass, as is common in householdmirrors. The first-surface mirror is usually precisely ground optically flat on its coatedside.
FLUORESCENCE: Simply stated. fluorescence is the conversion of invisible radiation, i.e.,ultraviolet, to visible white light. Thus. in a fluorescent tube, white light is producedwhen the ultraviolet light radiation strikes the phosphor coating on the inside of theglass envelope.
INFRARED: Infrared is a term used to define the portion of the electromagnetic spectrumthat lies between the visual zone and the short radio waves.
108
INTERFEROMETER: An instrument that useS interference bands created when twosections of a split light beam have been made to interfere with each other is called aninterferometer. In the case of the laser light interferometer, the light bands are spacedapproximately 12-1 /2 millionths of an inch.
LASER: The word “laser” originated from the process used to create the extremely brightlight, i.e., light amplification by stimulated emission of radiation. The term “laser” isalso applied to nonvisible radiating sources such as the carbon dioxide laser.
LASER LEVEL: This is a leveling instrument where a laser tube is attached to aconventional telescope. The beam is used as a reference. Some models use only a laser.tube. The laser beam in this case is made parallel with the axis of the spirit level.
MECHANICAL AXIS: The mechanical axis is a term used in optical work to define themechanical center of cylindrical housing or a lens: It is used in conjunction with theoptical axis when referring to the location of the lens elements of an alignmenttelescope or a cylindrical laser unit. The optical axis need not always be at themechanical axis, as in the case of simple lasers or telescopes.
MILLIWATT: The milliwatt, as its name implies. is one thousandth of a watt. Lasers usedin alignment have their output rated in milliwatts of power.
MIRROR, FIRST-SURFACE: See “first-surface mirror” in this glossary.
“MONOCHROMATIC: Monochromatic is a term derived from the Greek
meaning single, and chroma, meaning color. Thus. the helium-neon
words monos,laser beam is
monochromatic or a one-color light beam that is deep red and has a wavelength of6328 Angstroms.
NAS: The National Aerospace Standard (NAS) is a specification written by the AerospaceIndustry Association (AIA) of America. The NAS standard for alignment lasers andtelescopes defines the exact dimensions of the outer diameter of the cylindricalhousing.
OPTICAL AXIS: The optical center of a lens or lens system is called the optical axis. Theoptical centcr may or may not be coincident with the mechanical center.
PARALLAX ERROR: This is a term given to the angular error that results when two in-lineobjects are viewed from two different positions.
109
PHOTO CELL: The photo cell is a light-sensitive electronic devicecurrent when a light strikes its surface. In laser alignmentdetectors (targets) use silicone photo cells.
PRECISION LASER: This is another name for the alignment laser.
that produces a smallwork, the electronic
QUADRANT CELLS:one large siliconequadrant.
REFERENCE POINT:three-dimensional
The electronic, detectors used in laser alignment work have eithercell divided into four quadrants or four single cells arranged in a
A point located with specific dimensions. A reference point has aposition or location, i.e., elevation, longitudinal, and lateral, from
the surrounding structures.
SILVERED SURFACE: This term is commonly applied to the reflective coatings used inmirrors. Silver is used in specific types of mirrors used in scientific work, but mostmirrors use aluminum coatings.
SURVEYOR’S LEVEL: This is an optical instrument that uses a telescope with its opticalaxis adjusted parallel to a spirit level on the leveling base of the instrument.
TOOLING DOCK: The tooling dock is a rigidly fixed structure where optical instruments(lasers. alignment telescopes. transits, etc.) are precisely located to perform repeatedalignment tasks.
TOOLING LASER: Another name for alignment and precision lasers.
TRANSIT LASER: The transit laser has a cylindrical laser attached to the conventionaltransit telescope. Some models have the laser beam projecting through the opticaltelescope. Other models have the laser beam projecting parallel to the optical axis ofthe telescope.
ULTRAVIOLET: The term “ultraviolet” is the name given to the invisible portion of theelectromagnetic radiation spectrum, which is located just beyond the visible violet ofthe visual spectrum.
VISUAL TARGET: Any target not used for electronic sighting is a visual target.
laser beam detector. Rods ofdesired length measuring rod.
various length
